Great Internet Mersenne Prime Search

The Great Internet Mersenne Prime Search (GIMPS) is a collaborative project of volunteers who use freely available software to search for Mersenne prime numbers.

The GIMPS project was founded by George Woltman in 1996, who also wrote the software Prime95 and MPrime for the project. Scott Kurowski wrote the PrimeNet Internet server that supports the research to demonstrate Entropia-distributed computing software, a company he founded in 1997. GIMPS is registered as Mersenne Research, Inc. Kurowski is Executive Vice President and board director of Mersenne Research Inc. GIMPS is said to be one of the first large scale distributed computing projects over the Internet for research purposes.[1]

As of December 2018[update], the project has found a total of seventeen Mersenne primes, fifteen of which were the largest known prime number at their respective times of discovery. The largest known prime as of December 2018[ref] is 282,589,933 − 1 (or M82,589,933 in short). This prime was discovered on December 7, 2018 by Patrick Laroche.[2]

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The project began in early January 1996,[4][5] with a program that ran on i386 computers.[6][7]
The name for the project was coined by Luther Welsh, one of its earlier searchers and the co-discoverer of the 29th Mersenne prime.[8]
Within a few months, several dozen people had joined, and over a thousand by the end of the first year.[7][9]
Joel Armengaud, a participant, discovered the primality of M1,398,269 on November 13, 1996.[10]

As of October 2017[update], GIMPS has a sustained aggregate throughput of approximately 324 TeraFLOPS (or TFLOPS).[11] In November 2012, GIMPS maintained 95 TFLOPS,[12] theoretically earning the GIMPS virtual computer a rank of 330 among the TOP500 most powerful known computer systems in the world.[13] The preceding place was then held by an 'HP Cluster Platform 3000 BL460c G7' of Hewlett-Packard.[14] As of November 2014 TOP500 results, these old GIMPS numbers would no longer make the list.

Previously, this was approximately 50 TFLOPS in early 2010, 30 TFLOPS in mid-2008, 20 TFLOPS in mid-2006, and 14 TFLOPS in early 2004.

Although the GIMPS software's source code is publicly available,[15] technically it is not free software, since it has a restriction that users must abide by the project's distribution terms.[16]
Specifically, if the software is used to discover a prime number with at least 100,000,000 decimal digits, the user will only win $50,000 of the $150,000 prize offered by the Electronic Frontier Foundation.[16][17]

Third-party programs for testing Mersenne numbers, such as Mlucas and Glucas (for non-x86 systems), do not have this restriction.

GIMPS also "reserves the right to change this EULA without notice and with reasonable retroactive effect."[16]

^ † As of January 21, 2019[update], 46,251,389 is the largest exponent below which all other prime exponents have been checked twice, so it is not verified whether any undiscovered Mersenne primes exist between the 47th (M43112609) and the 51st (M82589933) on this chart; the ranking is therefore provisional. Furthermore, 82,104,823 is the largest exponent below which all other prime exponents have been tested at least once, so some Mersenne numbers below the 51st (M82589933) have to be tested.[19]

^ ‡ The number M82589933 has 24,862,048 decimal digits. To help visualize the size of this number, a standard word processor layout (50 lines per page, 75 digits per line) would require 6,629 pages to display it. If one were to print it out using standard printer paper, single-sided, it would require approximately 14 reams of paper.

Whenever a possible prime is reported to the server, it is verified first before it is announced. The importance of this was illustrated in 2003, when a false positive was reported to possibly be the 40th Mersenne prime but verification failed.[20]